Resist pattern forming method

A positive resist pattern forming method comprising:

• applying a photoresist, containing groups which generate carboxylic acid upon irradiation thereof, onto a semiconductor substrate;
• pre-baking the photoresist disposed on said semiconductor substrate, prior to exposing said photoresist to carboxylic acid generating irradiation, in an atmosphere containing water vapor, following the application step;
• exposing said pre-baked photoresist to irradiation under conditions sufficient to form carboxylic acid groups in said photoresist;
• heating the carboxylic acid containing photoresist following the exposure step;
• and
• developing the photoresist to remove the irradiated portions thereof following the heating step;
• wherein said step of pre-baking in said atmosphere containing water vapor is carried out under conditions sufficient to cause an increase in the amount of water in said pre-baked photoresist prior to said heating step, as compared to the amount of water which would have been in the same photoresist pre-baked under the same conditions but in the absence of said water vapor in said atmosphere during said pre-baking also prior to said heating step;
• wherein said atmosphere during baking has sufficient water vapor content, and is contacted with said resist coated semiconductor during pre-baking thereof under such conditions, as to increase the amount of water in said resist during exposure to said radiation;
• and
• wherein said increased amount of water in said pre-baked photoresist is sufficient to cause an increase in the speed of dissolution of a portion of said pre-baked photoresist which had been exposed to said irradiation.